Packaging machines are generally known in which a continuous web of material is converted into a plurality of individual pouches. The continuous web of material is folded in half over a plow to form two continuous side panels joined by a bottom fold. The folded web is passed through a series of seal bars which form transverse seals in between the side panels, thereby forming a strip of pouches interconnected by transverse seals. A cutter cuts through each transverse seal to form individual pouches with unsealed top edges. The individual pouches are transferred to a pouch filler, filled with product, and sealed. The sealed pouches are then collected for transport. Machines of this type may be categorized as either horizontal or vertical machines, depending on the general direction of web travel. The present invention relates to horizontal packaging machines in which the web travels horizontally.
The type and volume of product being packaged often determines whether the packaging process should use a continuously or intermittently advancing web. Certain products, such as hard candy, require a fill based on weight instead of volume. Scale fillers require relatively long period to fill a pouch. As a result, slower cycle continuous motion or intermittent motion is required to provide additional fill time. In addition, larger volume fills require more time, and therefore intermittent motion through the filler may be necessary. More free flowing products, such as sugar, may be dispensed using a diving funnel suitable for filling continuously advancing pouches.
In light of the above, packaging machines have been developed specifically for either intermittent or continuous operation. In intermittent motion machines, the web is intermittently advanced between dwell periods, and operations are performed on the web during the dwells. In a continuous web motion machine, on the other hand, the web continually moves at a set rate and each station for performing operations is phased with the web to perform the operation as the web passes through the station.
Most conventional packaging machines do not accurately form pouches out of weak or unsupported web materials. Conventional machines typically use a single pair of drive rolls to pull the web through the machine. As a result, weaker web materials stretch as they are pulled through the machine, thereby causing the pouch forming apparatus to be misaligned with the web. In addition, the web material must be sufficiently strong to withstand the force necessary to pull the web through the machine without breaking. These conventional packaging machines are therefore overly limited in the types of web material which may be run.
The problem of web stretch is exacerbated in conventional packaging machines using an intermittently advancing web. In intermittent operation, the web is repeatedly pulled and released as the web is advanced incrementally through the machine. The repeated pulls place a significant amount of strain on the web which tends to tear, break, or overly stretch weaker web materials.
A related problem with many conventional packaging machines is the need for an excessive amount of area in which to store a festoon of web material. Machines using intermittently advancing webs typically have a roll of web material which continually advances to reduce the stretch problems noted above. The continually advancing roll, however, requires storage space for excess web material during the dwells between incremental advances. Most machines having an intermittently advancing web therefore provide for a festoon area in which a buffer length of web material is stored. The conventional festoon sections typically employ a dancer roll which moves to accommodate the varying downstream web demand. The festoon sections are typically designed to store 4-5 repeat lengths of web material, thereby unduly extending the amount of floor space required for the machine.
Most conventional packaging machines further use a mechanical line shaft to drive the pouch forming components of the machine. As a result, extensive machining and retooling is often required to modify such machines to form different pouches. Furthermore, most or all of the machine is provided as an integral unit, with pouch forming operations running off of the mechanical drive line. As a result, individual components or groups of specific components may not be individually operated and tested.